Vertical filter

ABSTRACT

An improved vertical filtration unit which includes an airlift and a washbox designed for more efficient washing of dirt particles from the filtration material. The washbox consists of a filter media shield, and a washbox skirt for washing of the filtration material. A throttling valve on the wash water discharge line regulates the overall cleaning rate of the unit. The filtered liquid is discharged via a riser pipe which feeds into a filtered liquid box before exiting the filtration unit.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to methods and apparatus for filteringliquids containing suspended solids. Specifically, this inventionrelates to an improved vertical filtration unit.

[0003] 2. Background Art

[0004] The removal of suspended solids from liquids, especially water,has been a longstanding requirement for many uses of such liquids. Forexample, water which is free of suspended solids is greatly preferredfor uses such as drinking, industrial processing and swimming pools.Vertical filters, which utilize filter media such as sand, have beenused to separate suspended solids from water.

[0005] Vertical filters operate by introducing the liquid containingsuspended solids onto the top portion of a bed of filter media, usuallysand. As the liquid passes through the filter media under the force ofgravity, the suspended solids adhere to the filter media, allowingliquid free of suspended solids to accumulate and exit from the bottomof the vertical filtration unit.

[0006] The above-described method, although effective at removingsuspended solids from liquids, has several shortcomings.

[0007] The filter media eventually becomes saturated with suspendedsolids and no longer effectively removes suspended solids from theincoming liquid.

[0008] When the condition of (A) occurs, the vertical filtration unitmust cease operation so that the captured suspended solids can beremoved from the filter media. This removal is accomplished through anoperation referred to as “backwashing,” in which clean liquid isintroduced, under pressure, to the bottom of the filter media bed andpasses through the filter media in the reverse direction from thefiltration process. The reverse flow of the liquid removes the filteredsolids from the filter media and exits through the top of the verticalfilter. This operation is typically continued until the exiting backwashwater is free of suspended solids, indicating that the filter media isclean.

[0009] Backwashing can be very time consuming and generates largevolumes of wastewater.

[0010] Filtered solids are never completely removed from the filtermedial during backwashing which eventually results in the filter medianeeding to be replaced.

[0011] Filtration devices utilizing the above method are disclosed inU.S. Pat. No. 650,611.

[0012] The problem of backwashing filter media has been addressed, tosome extent, through the development of continuous, or moving bedfiltration systems. While these continuous filtration systems operate toremove suspended solids as outlined above, they have the added benefitof continuously removing filtered suspended solids from the filtermedia. In these methods, the dirtied filter media at the bottom of thevertical filter unit and a small amount of filtered water are airliftedto a washbox. This lifting is carried out by an airlift tube equippedwith a compressed air supply. The mixture of filtered water, filtrationsand and suspended solids is directed against a baffle or plate to scrubthe suspended solid particles from the sand.

[0013] The washed sand is returned to the top of the filter media bed.The suspended solid particles, washed from the filter media, are flushedfrom the filter by a combination of filter effluent liquid and filteredliquid that carry the suspended solids across a reject weir and out ofthe vertical filtration unit. The filtration cycle automatically repeatsitself with the influx of a new supply of liquid to be filtered.

[0014] Examples of the above-described continuous filtration systems aredisclosed and explained in U.S. Pat. No. 4,060,484, U.S. Pat. No.4,891,142 and U.S. Pat. No. 5,582,722, all of which are hereinincorporated by reference.

[0015] The above-described continuous systems for the filtration ofliquids and the removal of suspended solid particles are typically notas effective or efficient as industry and the public need and desire.These systems typically require level sensors and valve actuators whichare expensive and fail when electrical power supply is lost. Many valvesare often required which can cause confusion for those operating thefiltration unit. The airlifting operation often “plugs” with filtermedia, causing the filtration unit to be shut down for cleaning. Thereremains an unmet need to provide a reliable, maintenance-free,continuous, self-cleaning, vertical filtration unit for the removal ofsuspended solids from liquids.

SUMMARY OF THE INVENTION

[0016] In the liquid filtering apparatus of the present invention,liquid is filtered by its downward gravitational flow through a bed offilter media, usually, but not necessarily sand. The filter mediaremoves suspended solid particles from the liquid.

[0017] The filtered liquid is collected in a central filtered liquidcollection chamber. The filtered liquid exits the collection chamber toa filtered liquid riser pipe which terminates at an external filteredliquid box. The filtered liquid then exits the filtration unit.

[0018] The solids captured by the filter media are drawn downward withthe moving filter media bed into the suction area of an airlift. Thecaptured solids, filter media and a small portion of filtered liquid arelifted through the airlift being discharged into a washbox. Air isinjected into the airlift through a primary air manifold to effect theaction in the airlift.

[0019] In the washbox, the captured solids, filter media, and liquidmixture from the airlift hits a filter media shield hood and reflectsdownward into the interior of the washbox. In this area, a portion ofunfiltered liquid flows up from the bottom side of the washbox throughcleaning water inlet nozzles proportionally spaced around the bottomside of the washbox. This portion of influent liquid, or wash liquid,separates and suspends the captured solids from the filter media and ispiped by gravity to a dirtied liquid reject box.

[0020] The flow of wash liquid to the dirtied liquid reject box isregulated, for example, by a throttling valve. Thus, the overall flowrate through the liquid filtering apparatus may be controlled.

[0021] The wash liquid is then discharged from the dirtied liquid rejectbox.

[0022] The clean filter media is reintroduced to the top of the filtermedia bed. An alternative embodiment of the present invention utilizes atwo-stage washbox. In the two-stage washbox, the captured solids, filtermedia and liquid mixture from the airlift hits a filter media shieldhood and reflects downward onto a porous separation cone. The capturedsolids and liquid pass through the separation cone and into a dirtiedliquid reject collection tray. The captured solids and liquid are pipedby gravity to a dirtied liquid reject box. The filter media falls fromthe separation cone into the interior of the washbox. In the washboxinterior, the filter media is washed with unfiltered liquid, asdescribed above.

[0023] In a preferred embodiment of the present invention, the level offiltered liquid in the filtered liquid box is controlled by an overflowweir. The level of wash liquid in the dirtied liquid reject box iscontrolled by an overflow weir.

[0024] Still other objects of the present invention will become apparentto those of ordinary skill in the art upon reading and understanding thefollowing detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a schematic elevation view of the present inventionshowing internal components;

[0026]FIG. 2 is an isolation view of a two-stage cleaning washbox;

[0027]FIG. 3 is an isolation view of a one-stage cleaning washbox;

[0028]FIG. 4 is an isolation view of a washbox isolator; and

[0029]FIG. 5 is an isolation view of an airlift with a prime manifold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] In the following description and accompanying drawings, likereference numbers, as used in the various figures, refer to likefeatures or elements.

[0031] Referring to FIG. 1, filter unit 10 includes a vessel 11, whichis defined by legs 12 and a sidewall 13. While the vessel 11 is depictedas cylindrical in cross section, it may be square or some othercross-sectional configuration. Vessel 11 contains a bed of particulatefilter media 14, which may be sand, anthracite, ceramic beads, granularactivated carbon, or another suitable filtration material. The filtermedia 14 is classified prior to being placed in vessel 11. If filtermedia particles that are too fine are included, liquid flow through thebed can be impeded. If filter media particles are too large, theinternal parts can be damaged. It is preferred that the filter mediaparticle size is less than 0.125 inches.

[0032] Filter media bed 14 may have a double tapered conical shape andfilters an influent liquid 15 as it descends downwardly through thefilter media bed 14. Enhanced filtration is accomplished if the particlesize of the filter media bed 14 is coarser, or larger at the outer area,becoming finer, or smaller toward the middle and bottom of the filtermedia bed 14.

[0033] The upper conical configuration of the filter media bed 14 occursnaturally from the operation of the filtration unit. As the filter mediadrops from the washbox onto the top of the conical pile, the particlesclassify themselves. The larger filter media particles tend to roll downthe slope of the cone. The smaller particles, however, tend to descendvertically through the interior of the cone portion. This action resultsin the preferred, natural conical configuration of the pile.

[0034] The filtration process begins with the entry of the influentliquid 15 into the vessel 11 through influent liquid intake 16. Theinfluent liquid descends, due to gravity, through the conical filtermedia bed 14, toward the bottom of the filter. The influent liquid maybe any liquid but will typically be water or wastewater.

[0035] The unfiltered influent liquid 15 tends to flow through thecoarser outer layer rather than through the finer inner layer. Liquidstypically follow the path of least resistance. The path of leastresistance in this case is through the coarse particle size filter mediabecause the space between particles is large compared to the finerfilter media. Thus, the initial filtration of influent liquid 15 isaccomplished by the coarse particle size filter media.

[0036] The partially filtered influent liquid is further filtered as itnext flows through the interior layer of finer particle size filtermedia. The influent liquid then flows through multiple cylindricallyshaped cartridge screens 17 to an effluent chamber 18 which collects thefiltered liquid. The cartridge screens 17 surround effluent chamber 18.There must be a sufficient number of cartridge screens 17 to surroundeffluent chamber 18, typically, at least five cartridge screens areused. Preferred cartridge screens are pipe based screens with end caps,as sold by Tate Andale of Ontario, Canada. The filtered effluent liquidleaves the filtration unit through effluent line 19 to external effluentriser pipe 20. Filtered liquid value 45 can be used to take samples ofthe filtered liquid. The external effluent riser pipe 20 discharges intofiltered liquid box 21. The filtered liquid leaves the filtered liquidbox 21 through effluent line 23.

[0037] The height of filtered effluent liquid in filtered liquid box 21may be controlled by a filtered liquid overflow weir 22. This approachallows for easy measurement and control of the filtered liquid flowrate. The filtered effluent liquid flows over filtered liquid overflowweir 22 and leaves the filtered liquid box 21 through effluent line 23.

[0038] The solids captured by the filter media bed 14 are drawn downwardwith the moving filter media bed 14 into an intake 36 area of an airlift24. The continuous transport of dirty filter media from the bottom ofthe filter to a washbox 25 is carried out by the airlift 24. Theperformance of the filter unit depends, in great part, on theperformance of the airlift. Airlifts themselves are well known in thefields of wastewater treatment and well hydraulics. A conventionalairlift pump consists essentially of a vertical tube having its lowerend submerged in a liquid or slurry to be pumped. The upper end of thetube discharges the pump material. In the case of the present invention,the upwardly transported mixture of dirty filter media and filteredliquid empties into the washbox 25. The height to which the mixture canbe airlifted depends on the efficiency of the airlift system.

[0039] The actual pumping or lifting action is achieved by theintroduction of air into the lower part of the airlift 24 which alsocontains a mixture of filtered liquid and dirty filter media. Theresultant mixture is lighter than the liquid in which the lower end issubmerged. The upwardly directed pressure of the column of liquid in thebase of the airlift 24 combined with lower specific gravity of the air,liquid, and filter media mixture inside the airlift 24 forces themixture of dirty filter media and filtered liquid upward. As shown inFIG. 5, compressed air is introduced into the airlift 24 near its bottomthrough a primary air manifold 26. A prime air manifold 27 may be usedto help start the airlift process. Primary air manifold 26 communicateswith airlift 24 through passage 28. Prime air manifold 27 communicateswith airlift 24 through passage 29. Compressed air is supplied to theinterior of airlift 24 through the two manifolds 26, 27. The compressedair is supplied to primary air manifold 26 by compressed air line 46 andto prime air manifold 27 by compressed air line 47, both of whichcommunicate with a source of compressed air (not shown) in order tomaximize the air flow rate to the mixture being airlifted to washbox 25.The prime air manifold passage 29 is located above the primary airmanifold 28. The airlift tube may have a bell-shaped bottom intake 36.This bell-shaped bottom intake increases the pumping rate. Thus, morefiltered water, filter media and dirt can be pumped to the top of thefiltration unit without increasing the air supply requirement.

[0040]FIG. 3 illustrates the construction of a one-stage washbox 25.Airlift 24 is centered within washbox 25 through the use of centeringguides 55. The air, liquid, and filter media mixture rises through theairlift 24 and deflects from a filter media shield hood 41 into awashbox body 35. All cleaning is accomplished by influent liquid 42 thatenters the washbox body 35 through cleaning liquid inlet nozzles 32 asshown in FIG. 4. There can be any number of cleaning liquid inletnozzles 32. It is preferred that the cleaning liquid inlet nozzles 32 beproportionately spaced on the underside of washbox skirt 34. Thepreferred number of cleaning liquid inlet nozzles 32 is three. Thecleaning liquid inlet nozzles 32 may alternatively be supplied, at leastin part, with filtered liquid from the filtered liquid box.

[0041] The higher density filter media settles into the washbox skirtarea 34. In this area, the influent liquid flows up from the bottom ofthe washbox skirt 34 via cleaning liquid inlet nozzles 32.

[0042] Influent liquid 42, or wash liquid, enters a washbox filter medialiquid separation area 31 via cleaning liquid inlet nozzles 32; there isa pressure difference between the liquid level in vessel 11, and a dirtyliquid reject line 33. The action of this pressure differential urgesthe wash liquid out dirty liquid reject line 33 and provides automaticlevel control, eliminating the need for level sensors in the operationof the vertical filter of the present invention. The upward velocity ofwash liquid keeps the lower density solids in suspension so they can beslurried and discharged to the dirtied liquid reject box 30. This slurryof solids and liquid is transported to the dirtied liquid reject box 30via the dirtied liquid reject line 33.

[0043] Due to its higher density, the filter media settles in thewashbox skirt 34. The wash liquid thus flows upward through anincreasingly settled area of filter media before it reaches the dirtiedliquid reject line 33. The filter media is thus cleaned at the washboxskirt area 34 before settling back to the top of the filter media bed 14via washbox isolator 39. The washbox isolator 39 has a reducing, taperedportion at its lowermost point and reintroduces the filter media to theupper region of the filter media bed 14. This maintais the generallyconical configuration of the bed.

[0044] The wash liquid discharges out of the dirtied liquid reject box30 via dirtied liquid effluent line 40. A throttling valve 44 on thedirtied liquid reject line 33 may be used to adjust the flow rate of thewash liquid out of dirtied liquid reject box 30 by adjusting the flow indirtied liquid reject line 33. Alternatively, a plate with an orificesized appropriately to the system requirements can be used to regulatethe flow in dirtied liquid reject line 33. Controlling the wash waterflow rate is important in that too high of a flow rate can result incarryover of the filter media. Too slow of a flow rate can result ininsufficient cleaning of the filter media.

[0045] The level of wash liquid in dirtied liquid reject box 30 may becontrolled by a reject weir 37. The liquid level in the filtration unitvessel 11 will change accordingly with filtration head loss. Thus,reject weir 37 aids throttling valve 44 in the automatic level controlfeature of the vertical filter of the present invention. The flow rateof wash liquid will automatically change with the head loss or cleaningrequirement within a desired reject rate range of four percent (4%) toseven percent (7%). The reject rate is the ratio of wash liquid effluentflow to influent liquid flow. This method eliminates the need forelectronic level control systems, simplifies operation compared toprevious vertical filters by having fewer valves, and allows the flowrate of wash liquid to be changed as the requirement for cleaning thefilter media changes.

[0046] An alternative two-stage cleaning washbox apparatus is depictedin FIG. 2. In this scenario, the two-stage cleaning washbox 53 includesa filter media shield hood 48 which deflects the filtered liquid anddirty filter media downwardly onto a separation cone 49. This downwarddeflection efficiently washes dirt particles and solids from the filtermedia, along with the filtered liquid. The solids concentrated liquidfrom the airlift drops on the inclined porous surface of the separationcone 49 and passes through the surface of separation cone 49 into adirtied liquid reject collecting tray 51. The separation cone 49 isconstructed of a porous media or material. A woven, wedge wireconstruction is preferred for separation cone 49. The preferred wedgewire construction is such that the flat side of the wedge wire facesoutward. The gap between the horizontally oriented wedge wire strands isup to 0.02 inches. The concentrated dirty liquid reject stream is pipedby gravity through line 43 to the dirtied liquid reject box 30. This isthe first wash stage.

[0047] The dewatered, partially cleaned, filter media moves down alongthe surface of the separation cone 49 and falls into a washbox filtermedia liquid separation area 50 and eventually into the washbox skirt 52and is washed clean of filtered particles as described in theabove-mentioned one-stage washbox 25 by unfiltered liquid, now washliquid, entering into washbox skirt 52 via inlet nozzles 54. The washliquid is then carried away by the dirtied liquid reject line 33. Thisis the second wash stage. The wash liquid from line 33 is then carriedto the dirtied liquid reject box 30 where it is then removed from thefilter unit as described above. Likewise, the dirtied liquid reject ratemay be controlled by a throttling valve 44 on dirtied liquid reject line33 as described in connection with the one-stage washbox 25.

[0048] The present invention is also directed to a method of filteringliquids. The preferred method will generally include the steps of:

[0049] providing a bed of filtration material, usually sand, comprisingparticles of different sizes, including large particles and fineparticles, the bed having a general conical configuration;

[0050] introducing unfiltered liquid, typically water or wastewater,above the bed, which liquid is filtered through the bed in a downwarddirection, the unfiltered liquid passing through multi-cartridge screensinto an effluent chamber to form a collection of filtered liquid;

[0051] removing the filtered liquid from the effluent chamber,transporting the filtered liquid through a riser pipe to a filteredliquid box wherein the flow and height of the filtered liquid iscontrolled by a weir, the filtered liquid flowing over the weir andexiting the filtered liquid box;

[0052] withdrawing dirty filtration material from the lower region ofthe bed;

[0053] transporting the dirty filtration material with a portion of thefiltered liquid from a position in the lower region of the bed to aposition above the bed;

[0054] separating dirt from the filtration material by deflecting thedirty filtration material and filtered liquid off of a filter mediashield hood;

[0055] washing the filtration material by introducing a portion ofunfiltered liquid at the bottom side of a washbox skirt in acounter-current manner, transporting the unfiltered liquid, now washliquid, through the filtration material in the washbox skirt;

[0056] transporting the wash liquid to a dirtied liquid reject box;

[0057] regulating the flow of the wash liquid to the dirtied liquidreject box by use of a throttling valve;

[0058] discharging the wash liquid from the dirtied liquid reject box;and

[0059] depositing clean filtration material to the top of the bed so asto maintain the generally conical configuration.

[0060] An alternative preferred method, using two-stage washing, willgenerally include the steps of:

[0061] providing a bed of filtration material, typically sand,comprising particles of different sizes, including large particles andfine particles, the bed having a general conical configuration;

[0062] introducing unfiltered liquid, typically water or wastewater,above the bed, which liquid is filtered through the bed in a downwarddirection, the then filtered liquid passing through multi-cartridgescreens into an effluent chamber to form a collection of filteredliquid;

[0063] removing the filtered liquid from the effluent chamber,transporting the filtered liquid through a riser pipe to a filteredliquid box wherein the height of the filtered liquid is controlled by aweir, the filtered liquid flowing over the weir and exiting the filteredliquid box;

[0064] withdrawing dirty filtration material from the lower region ofthe bed;

[0065] transporting the dirty filtration material with a portion of thefiltered liquid from a position in the lower region of the bed to aposition above the bed;

[0066] separating dirt from the filtration material by deflecting thedirty filtration material and filtered liquid off of a filter mediashield hood, collecting filtration material on a porous surface, such asa wedge wire or metal wire mesh screen cone, transporting dirt ladenfiltered liquid through the porous surface, collecting the dirt ladenscreened liquid in a reject liquid collection tray;

[0067] conveying filtration material from the porous surface to awashbox skirt;

[0068] washing the filtration material in the washbox skirt byintroducing a portion of unfiltered liquid at the bottom side of thewashbox skirt, transporting the unfiltered liquid, now wash liquid,through the filtration material in the washbox skirt;

[0069] transporting the wash liquid and the dirt laden filtered liquidto a dirtied liquid reject box;

[0070] regulating the flow of the wash liquid to the dirtied liquidreject box by use of a throttling valve;

[0071] discharging the wash liquid and the dirt laden filtered liquidfrom the dirtied reject liquid box; and

[0072] depositing clean filtration material to the top of the bed so asto maintain the generally conical configuration.

[0073] Alternatively, the wash liquid in the washbox skirt may befiltered water supplied from the filtered liquid box.

[0074] The invention has been described with reference to the preferredembodiments. Obvious modifications and alterations will occur to othersupon reading and understanding the preceding detailed description. It isintended that the invention be construed as including all suchmodifications and alterations insofar as they come within the scope ofappended claims or the equivalents thereof.

I claim:
 1. A liquid filtering apparatus comprising: a vessel; a bed offiltration material within said vessel; an intake for introducing intoan upper region of said vessel an influent liquid to be filtered, saidliquid being filtered by gravitationally descending through the bed to alower region of said vessel; an enclosure in said bed for collectingsaid filtered liquid; an outlet for transporting said filtered liquidfrom said enclosure; an airlifting tube for conveying a mixture of saidfiltration material dirtied by particulates taken from said liquid to befiltered and a portion of said filtered liquid from the lower region ofsaid vessel to the upper region of said vessel, said airlifting tubeterminating at a washbox; said washbox comprising a filter media shieldhood for deflecting said dirtied filtration material; a washbox skirtbelow said filter media shield hood wherein said filtration material iswashed with a portion of said influent liquid entering into said washboxskirt through at least one cleaning water inlet nozzle; a washboxisolator at the bottom of said washbox skirt through which the washedfiltration material is reintroduced to an upper region of said bed; adirtied liquid reject line for conveying from the washbox, the influentliquid which has washed the filtration material; and means forintroducing a primary gas to said airlifting tube to induce flow of saiddirtied filtration material to said washbox.
 2. The liquid filteringapparatus according to claim 1, wherein the filtration material isselected from the group consisting of sand, anthracite, ceramic beadsand granular activated carbon.
 3. The liquid filtering apparatus ofclaim 1, wherein the liquid is water or wastewater.
 4. The liquidfiltering apparatus of claim 1, wherein the intake at the lower end ofsaid airlifting tube is a hollow bell-bottom shape.
 5. The liquidfiltering apparatus of claim 1, wherein an airlift primer line iscommunicated to said airlifting tube at a location above said means forintroducing primary gas, said airlift primer line being connected to acompressed gas source.
 6. The liquid filtering apparatus of claim 1including a valve on said dirtied liquid reject line for adjusting theflow rate of liquid therethrough.
 7. The liquid filtering apparatus ofclaim 1 including a filtered liquid box connected to said outlet, saidfiltered liquid box having a weir positioned in said filtered liquid boxto control the level of filtered liquid therein.
 8. The liquid filteringapparatus of claim 1 including a dirtied liquid reject box connected tosaid dirtied liquid reject line, said dirtied liquid reject box having aweir to control the level of liquid in said dirtied liquid reject box.9. The liquid filtering apparatus of claim 1 including a plurality ofmulti-cartridge screens said filtered liquid passing through saidmulti-cartridge screens before entering said enclosure.
 10. A liquidfiltering apparatus comprising: a vessel; a bed of filtration materialwithin said vessel; an intake for introducing into an upper region ofsaid vessel a liquid to be filtered, said liquid being filtered bygravitationally descending through the bed to a lower region of saidvessel; an enclosure in said bed for collecting said filtered liquid;said filtered liquid entering said enclosure through multi-cartridgescreens in the lower region of said vessel; an outlet for transportingsaid filtered liquid from said enclosure to an effluent riser pipe, saideffluent riser pipe terminating at a filtered liquid box, the level ofsaid filtered liquid in said filtered liquid box being controlled by aweir, said filtered liquid passing over said weir and exiting saidfiltered liquid box; an airlifting tube for conveying a mixture of saidfiltration material dirtied by particulates taken from said liquid to befiltered and a portion of said filtered liquid from the lower region ofsaid vessel to the upper region of said vessel, said airlifting tubeterminating at a washbox; said washbox comprising a filter media shieldhood for deflecting said dirtied filtration material, a washbox skirtbelow said filter media shield hood; a washbox isolator, at the bottomof said washbox skirt, whereby the washed filtration material isreintroduced to the upper region of said bed and wherein, saidfiltration material is washed with a small portion of said influentliquid, now wash liquid, entering into said washbox skirt throughcleaning water inlet nozzles located at the bottom of said washboxskirt; a dirtied liquid reject line conveying the wash liquid from saidwashbox to a dirtied liquid reject box; a valve near the terminus ofsaid dirtied liquid reject line for adjusting said wash liquid flowrate; said dirtied liquid reject box comprising a weir to control theheight of said wash liquid in said dirtied liquid reject box and anoutlet for said wash liquid to exit said dirtied liquid reject box; andmeans for introducing a primary gas to said airlifting tube to induceflow of said dirtied filtration material to said washbox.
 11. The liquidfiltering apparatus according to claim 10, wherein the filtrationmaterial includes sand.
 12. The liquid filtering apparatus of claim 10,wherein the liquid is water or wastewater.
 13. The liquid filteringapparatus of claim 10, wherein the intake at the lower end of saidairlifting tube is a hollow bell-bottom shape.
 14. The liquid filteringapparatus of claim 10, wherein an airlift primer line is communicated tosaid air lifting tube at a location above said means for introducing aprimary gas, said airlift primer line being connected to a compressedgas source.
 15. A liquid filtering apparatus comprising: a vessel; a bedof filtration material within said vessel; an intake for introducinginto an upper region of said vessel a liquid to be filtered, said liquidbeing filtered by gravitationally descending through the bed to a lowerregion of said vessel; an enclosure in said bed for collecting saidfiltered liquid; an outlet for transporting said filtered liquid fromsaid enclosure to an effluent riser pipe, said effluent riser pipeterminating at a filtered liquid box; an airlifting tube for conveying amixture of said filtration material dirtied by particulates taken fromsaid liquid to be filtered and a portion of said filtered liquid fromthe lower region of said vessel to the upper region of said vessel, saidairlifting tube terminating at a washbox; said washbox comprising afilter media shield hood for deflecting said dirtied filtrationmaterial, a porous separation cone below said filter media shield hoodfor separating said filtration material from said particulates and saidfiltered liquid, a dirtied liquid reject collection tray below saidseparation cone for collecting particulates and liquid which have passedthrough said separation cone; a washbox skirt below said dirtied liquidreject collection tray; a washbox isolator at the bottom of said washboxskirt whereby the washed filtration material is reintroduced to theupper region of said bed and wherein said filtration material is washedwith a portion of said filtered liquid entering into said washbox skirtthrough cleaning water inlet nozzles located at the bottom of saidwashbox skirt; a first dirtied liquid reject line communicating saiddirtied liquid reject collection tray with a dirtied liquid reject box;a second dirtied liquid reject line conveying said wash liquid from saidwashbox to the dirtied liquid reject box; and means for introducing aprimary gas to said airlifting tube to induce flow of said dirtiedfiltration material to said washbox.
 16. The liquid filtering apparatusaccording to claim 15, wherein the filtration material is selected fromthe group consisting of sand, anthracite, ceramic beads and granularactivated carbon.
 17. The liquid filtering apparatus of claim 15,wherein the liquid is water or wastewater.
 18. The liquid filteringapparatus of claim 15, wherein the intake at the lower end of saidairlifting tube is a hollow bell-bottom shape.
 19. The liquid filteringapparatus of claim 15, wherein an airlift primer line is communicated tosaid airlifting tube at a location above said means for introducingprimary gas, said airlift primer line being connected to a compressedgas source.
 20. The liquid filtering apparatus of claim 15 including avalve on said dirtied liquid reject line for adjusting the flow rate ofsaid wash liquid.
 21. The liquid filtering apparatus of claim 15,wherein a weir is positioned in said filtered liquid box to control thelevel of said filtered liquid therein.
 22. The liquid filteringapparatus of claim 15, wherein a weir is positioned in dirtied liquidreject box to control the level of said wash liquid in said dirtiedliquid reject box.
 23. The liquid filtering apparatus of claim 15,wherein said filtered liquid first passes through multi-cartridgescreens before entering said enclosure.
 24. The liquid filteringapparatus according to claim 18, wherein said separation cone isconstructed of wedge wire.
 25. A method of filtering a liquid comprisingthe steps of: providing a bed of filtration material; introducingunfiltered liquid above said bed, which liquid is filtered through saidbed in a downward direction, said unfiltered liquid passing into achamber for collecting filtered liquid; removing said filtered liquidfrom said chamber for collecting filtered liquid, transporting saidfiltered liquid through a riser pipe to a filtered liquid box, saidfiltered liquid then exiting said filtered liquid box; withdrawing dirtyfiltration material from the lower region of said bed; transporting saiddirty filtration material with a portion of said filtered liquid from aposition in the lower region of said bed to a position above said bed;separating dirt from said filtration material by deflecting said dirtyfiltration material and filtered liquid off of a filter media shieldhood; washing said filtration material by introducing acounter-directional flow of said unfiltered liquid, and transportingsaid unfiltered liquid, now wash liquid, through said filtrationmaterial; transporting said wash liquid to a dirtied liquid reject box;discharging said wash liquid from said dirtied liquid reject box; anddepositing clean filtration material from said washbox skirt to the topof said bed.
 26. The method of claim 25, wherein the filtration materialis selected from the group consisting of sand, anthracite, ceramic beadsand granular activated carbon.
 27. The method of claim 25, wherein theunfiltered liquid is water or wastewater.
 28. The method of claim 25,wherein said filtered liquid in said filtered liquid box passes over aweir prior to exiting said filtered liquid box.
 29. The method of claim25, wherein the flow of said wash liquid to said dirtied liquid rejectbox is controlled by a throttling valve.
 30. The method of claim 25,wherein said wash liquid in said dirtied liquid reject box passes over aweir prior to exiting said dirtied liquid reject box.
 31. A method offiltering a liquid comprising the steps of: providing a bed offiltration material; introducing unfiltered liquid above said bed, whichliquid is filtered through said bed in a downward direction, saidfiltered liquid passing through screens into a chamber for collectingfiltered liquid; removing said filtered liquid from said chamber forcollecting filtered liquid, transporting said filtered liquid through ariser pipe to a filtered liquid box wherein the flow and height of saidfiltered liquid is controlled by a weir, said filtered liquid flowingover said weir and exiting said filtered liquid box; withdrawing dirtyfiltration material from the lower region of said bed; transporting saiddirty filtration material with a small portion of said filtered liquidfrom a position in the lower region of the bed to a washbox positionedabove the bed; separating dirt from the filtration material bydeflecting said dirty filtration material and filtered liquid off of afilter media shield hood; washing said filtration material in saidwashbox by introducing a counter-directional flow of said unfilteredliquid to a bottom side of said washbox, transporting said unfilteredliquid, now wash liquid, through said filtration material in saidwashbox; transporting said wash liquid to a dirtied liquid reject box;regulating the flow of said wash liquid to said dirtied liquid rejectbox; discharging said wash liquid from said dirtied liquid reject box;depositing clean filtration material from said washbox to the top ofsaid bed.
 32. The method of claim 31, wherein the filtration material isselected from the group consisting of sand, anthracite, ceramic beadsand granular activated carbon.
 33. The method of claim 31, wherein theunfiltered liquid is water or wastewater.
 34. A method of filtering aliquid comprising the steps of: providing a bed of filtration material;introducing unfiltered liquid above said bed, which liquid is filteredthrough said bed in a downward direction, said unfiltered liquid passinginto a chamber for collecting filtered liquid; removing said filteredliquid from said chamber for collecting filtered liquid, transportingsaid filtered liquid through a riser pipe to a filtered liquid box, saidfiltered liquid then exiting said filtered liquid box; withdrawing dirtyfiltration material from the lower region of said bed; transporting saiddirty filtration material with a portion of said filtered liquid from aposition in the lower region of the bed to a position above the bed;separating dirt from the filtration material by deflecting said dirtyfiltration material and filtered liquid off of a filter media shieldhood, passing filtration material over a porous surface, transportingdirt laden filtered liquid through said porous surface, collecting saiddirt laden filtered liquid in a reject liquid collection tray; conveyingfiltration material from said porous surface to a washbox skirt; washingsaid filtration material in said washbox skirt by introducing a portionof said unfiltered liquid at a bottom side of said washbox skirt,transporting said unfiltered liquid, now wash liquid, through saidfiltration material in said washbox skirt in a counter-current manner;transporting said wash liquid and said dirt laden filtered liquid to adirtied liquid reject box; regulating the flow of said wash liquid tosaid dirtied liquid reject box by use of a throttling valve; dischargingsaid wash liquid and said dirt laden filtered liquid from said dirtiedliquid reject box; and depositing clean filtration material from saidwashbox skirt to the top of the bed.
 35. The method of claim 34,including the step of passing the filtered liquid over a weir prior toexiting the filtered liquid box.
 36. The method of claim 34, includingthe step of passing the wash liquid and dirt laden filtered liquid overa weir prior to exiting the dirtied liquid reject box.
 37. The method ofclaim 34 wherein said wash liquid in said washbox is introduced, atleast in part, as filtered liquid from said filtered liquid box.